Coolant filtration systems and methods for use thereof are well known in the metalworking industry. An example of a filtration system for one type of metalworking machine is disclosed in Urban, U.S. Pat. No. 8,501,017, issued Aug. 6, 2013. The Urban system includes a housing, pump, conveyor assembly, drum assembly and centrifugal separator. The housing includes a tank for receiving and holding coolant coming out of one or more of the metalworking machines. The pump is used to drive the coolant through the coolant filtration system. One part of the conveyor assembly is disposed within a housing in order to carry away workpiece chips from the coolant. The drum assembly is located near the conveyor assembly, for purposes of filtering the coolant. The centrifugal separator receives coolant processed by the conveyor and drum assemblies. Filters are provided for additional filtering of the coolant which is output from the centrifugal separator.
Another process and apparatus for treating liquid coolant is disclosed in Brandt, U.S. Pat. No. 3,897,335, issued Jul. 29, 1975. The Brandt patent discloses a continuous process for bleeding off a portion of a clean aqueous based coolant containing water, oil and additives from a central cooling system. The bleed-off is made into a heated and substantially quiescent pool for purposes of killing bacteria. The heat also breaks out mechanically emulsified tramp oil from the coolant, which is then skimmed off. The heat also frees some of the solid contaminants for removal, and essentially “tightens” the chemically emulsified oils. The result of substantially sterilized and cleaned coolant is then returned to the central cooling system.
Brandt also discloses the use of a bypass valve in an output duct from the return pump for the cooling system. A heat exchanger is used with the bypassed coolant, and a settling tank is also provided, where the heater is located. A skimmer is also provided for the separated tramp oil and flotsam from the tank. The tank can also include a bottom scraper for heavier fine particles or solid contaminants that may settle in the tank. From the settling tank, the clean and sterilized coolant can be pumped to a clean tank. Alternatively, the coolant can then be pumped to a mixer for make-up materials before passing through the heat exchanger and being returned to the coolant system. Other grinding apparatus deploying cooling systems are disclosed in European Patent Application 2,578,360 and U.S. Pat. No. 6,123,606.
Referring more specifically to background related to the current invention, the coolant which is used to cool a tool and/or workpiece in a machining operation (such as grinding) becomes contaminated with metallic particles which are commonly referred to as “swarf.” The swarf comprises metallic particles specifically removed by the tool/grinder and the abrasive fragments which may have come from the tool/grinder itself. The used coolant needs to be filtered before it can be recycled in the operation or, alternatively, discarded.
As known in the industry, after the used coolant has passed through a magnetic separator for purposes of removing larger metallic particulate, the coolant is passed directly through a paper filtration system which is then used to remove the non-magnetic particulate and to achieve what is known in the industry as a required 10 um filtration. In this operation, the dirty coolant is pulled through a paper media with a pump. This process produces a “cake” which is formed at the layer of built up “swarf” or “grinding fines” on the paper. The coolant, after being pulled through the paper media, is recycled in the operation or discarded. Typically, the paper media (with the cake) is discarded into a landfill.
A partially schematic diagram of a prior art system utilizing a coolant filtration process is illustrated in FIG. 1. The system is identified as system 100. The system 100 includes what is shown on the left side of the diagram as a clean tank 102. The clean coolant is pulled from the clean tank 102 through the use of a pump 104. The pump 104 is utilized to feed the coolant to grinding stones through pipes 105, which are typically of a size having a three-inch diameter. The coolant is fed to the pad grinder 106 where a conventional pad grinding operation may be continuously executed. During the pad grinding operation, the coolant is used to carry away grinding swarf of cast iron and CBN. The dirty coolant then flows back through a pipe 108, with the coolant fed through a pump pack pump 110. The pipe 108 leads the dirty coolant to a magnetic separator 112. The magnetic separator 112 is utilized to remove approximately 50 percent of the grinding swarf.
Following the magnetic separation process carried out through the separator 112, the coolant then flows through a trough 114 to what is characterized as a dirty tank 116. When the coolant is in the dirty tank 116, the same is pulled through the paper media 118. With the coolant fluid flowing through the paper media 118, a cake of grinding swarf is formed on the paper 118.
With this process, the paper media will reach a point where it cannot pull a sufficient amount of coolant through the media 118. When this threshold occurs, an indexer 120 is utilized to index the paper media 118 within the dirty tank 116 to a clean section of paper 118. The dirty paper is then applied to a collector 122 and sent to a landfill or the like for disposition.
With a system such as described above, several concerns arise. First, a safety issue arises in that the caked and dirty paper is relatively heavy and difficult to remove from the machine. Also, quality issues arise in that the paper media 118 allows some of the swarf to pass through the system. This swarf can readily cause damage to locators and cause relatively shortened tool life.
Still further, costs present principal concerns. In a conventional operation, the yearly cost of paper media may exceed $200,000. Costs for using landfill are often in the range of approximately $5,000. In addition, if damage is caused to pumps and the like, rebuilding costs can be significant. A sample supply pump rebuild can be in the order of $6,000 or more.
Environmental concerns exist with respect to dirt which results from handling of the used, caked paper media and from splatter from the paper. In addition, concerns exist with respect to damage to the environment as a result of the caked, dirty paper going into the landfill. In addition, with respect to system delivery and up time, the prior art system requires substantial maintenance with respect to fluid replacement and the like. Also, down time of the grinders results in significant production loss.